Casters are widely used for to provide rolling support for a variety of objects including carts, moving dollies, convertible hand trucks, tool chests, hydraulic floor jacks, appliances, chairs, stools, bed frames, and the like. Typically, a plurality of casters are used to support an object, typically positioned at corner positions of a bottom surface of the object or, if the object has downwardly extending legs, affixed to the bottom surfaces of each leg. For some objects, like an appliance, a plurality of casters may be affixed directly to a bottom of the appliance frame and the appliance represents the load supported by the casters, i.e., the casters affixed to the bottom of a washing machine frame support the weight of the washing machine and allow for rolling movement of the washing machine along a basement floor. For other objects, like a moving dolly, the casters are affixed to a support platform. The support platform of the moving dolly or a plurality of moving dollies, in turn, are used to support and move a heavy object, such as a piano or desk.
A caster typically includes a hard plastic or rubber or pneumatic wheel mounted on a horizontally-oriented wheel axle allowing the caster wheel to roll about a horizontal axis of rotation (horizontal rotational axis) across a surface, such as a floor. Casters are typically sold in two configurations—swiveling and fixed. In a swiveling configuration, the caster wheel is free to swivel about a vertical rotational axis or swivel axis defined by a rotational connection between a stationary plate assembly and a rotatable yoke assembly to which the caster wheel is mounted. The plate assembly is typically affixed to an object, such as a support platform (moving dolly), a bottom of an appliance frame or a leg of a chair or stool. In the swiveling configuration, the caster yoke assembly is able to swivel about the swivel axis with respect to the plate assembly and the caster wheel is able to rotate about the horizontal rotational axis so that the caster can simultaneously swivel and roll so that the caster wheel may move in any desired direction along a floor.
In the rigid configuration, the caster wheel is fixed in a given rotational orientation with respect to the plate assembly. Thus, the caster wheel is constrained to move or roll about the horizontal rotational axis in a single linear direction, i.e., forward or backward, only.
Depending on the nature of the load to be moved and the desired path travel for moving the load; it may be desirable to have a caster that is convertible between use in a swiveling configuration and use in a rigid configuration.